just another 300 cartridge

[pug]

I was curious if there was any interest in another 308/223 based cartridge for the AR-15 or any other .223 platform. Not really for subsonic use because of increased case capacity but suited ideally for (supersonic) 125 to 150 gr bullets yet all the heavys can be used as well. Calculated power shows higher than 7.69x39 for same bullet weight but that can be off somewhat. This isn't a money maker because I don't make barrels for sale. I am just wondering what everyone thought.

[Spook]

Pug , I've actually formed up a few 30 TCU's...I was thinking the old 147grain steel core milsurp for an AR -pistol or SBR ,what shoulder angle were you looking at? There's a load a Reloadersnest for 150's at just over 2100 FPS!
The 7mm TCU was always pretty accurate even at distance out of TC's.

[pug]

Spook you are talking about a whole lot more case capacity than I am. The guy at the shop shoots TCU and the cases are a little long for what I had in mind. I was looking more at a 30 degree shoulder and case capacity just shy of 25 grains. In order for the cartridge to run fairly smooth at full auto rates the cartridges must stack correctly in the magazine and that is why I think I would go with a shorter case. As far as velocity I am not going to guess although the computer that doesn't always know what it is talking about says over 2200 fps for a safe load out of a 16" barrel. It also says pressures can go up to a max of 70,000 psi so I don't think there is a problem of not enough pressure. I got the cartridges made up and most of the specs filled out but I may still lengthen the neck.

You know I looked at over 75 different 308 cartridges and still didn't see the 30 TCU which I knew about. I was also surprised to see the 30-223 had less case capacity than the 300/221.

Not sure this was the right place to post this subject so forgive me if I made a booboo.

[pug]

Spook here is a picture of the cartridge with a 150gr FMJBT seated to 2.200" compared to a 300/221 on the left. I was initially testing mags with magpul followers and everything stacks fine but green GIs cause a little more drag.

[Spook]

Pug, I cant see a pic?

[320pf]

Pug,

I would like to see the picture. Somehow the picture did not come throught with your post.

320pf